The present invention is directed to the processing of semiconductor and more particularly to the processing of greensheets used to make ceramic substrates for microelectronic components.
In the ceramic electronics industry, multilayer ceramic (MLC) technology is typically used to create three-dimensional circuitry in ceramic substrates for microelectronic devices such as integrated circuits and ceramic capacitors. The three-dimensional circuitry in the ceramic substrate is made by applying a conductive material in a circuit pattern on a ceramic/polymer composite sheet. The ceramic/polymer composite sheet is known as a xe2x80x9cgreensheetxe2x80x9d and may have a number of via holes punched in it to allow vertical connection between the conductive material on adjacent sheets. After the vias are punched, the greensheets are screened and patterned by applying a conductive paste into the via holes and along the surface of the greensheet. The screening is typically done utilizing a mask applied over the individual greensheet. The greensheets are then generally stacked in a designated order and laminated together under appropriate heat and pressure to form a laminate which can be handled as a unified structure. To produce the final ceramic material, the laminated ceramic/polymer composite is fired, i.e. heated, to remove the polymer, followed by heating to higher temperature to sinter and densify the ceramic. MLC technology has developed to incorporate advanced technologies and groundrules, i.e., triple dense conductors, thin green sheets and large area greensheets. However, in the course of adopting such new technologies, greensheet stability has become a concern. In particular, radial error of the through holes can and does contribute to misalignment of the conductive vias and other features. The radial error is the radial distance between the actual location of the via and the design location of the via. The reference is arbitrarily set but the center of the pattern is usually chosen. The use of one or more of these advanced technologies in a multilayer package, where the individually punched and screened sheets are stacked adjacent to each other to form the laminate, is possible only if the via holes can be punched and screened with a small radial error. It would be especially desirable if this radial error were less than 30 microns. Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved via-punched and screened greensheet for use with advanced groundrules, thin green sheets and large area greensheets. It is another object of the present invention to provide an improved greensheet and processing method which reduces radial error of the screened greensheet. A further object of the invention is to provide a process and system to make greensheet via alignment more precise in stacked greensheet laminates.
It is an object of the invention to provide a screening method which reduces the greensheet shrinkage caused by the drying of the via paste. It is another object of the instant invention to provide a method of strengthening thin greensheets for better performance. It is yet another object of the instant invention to provide a method of processing uncured greensheets.
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a method of processing greensheets, wherein the user provides a greensheet having a width, length, thickness, a first side and a second side, then bonding the first side of the greensheet at least one strip, wherein the strip lies in a first plane, then bonding to the second side of the green sheet at least one strip, wherein the strip lies in a second plane, then processing the greensheet; and finally removing the strips from the processed greensheet.